Discovery of an emission in NO++

Abstract

Doubly charged NO+ + ions were produced by double photoionization of neutral nitric oxide molecules with the synchrotron radiation from ACO as a photon source of variable energy in the 35–68 eV range. Two stable states of NO+ + were observed in the double photoionization spectrum with energies of 38.6 and 40.0 eV. An emission from NO+ + was discovered by using a new photoion–photon of fluorescence coincidence (PIFCO) experiment. The fluorescence efficiency was measured as a function of the excitation energy, indicating that the emitting state, whose onset energy was observed at 42.5 eV, is a stable or slowly predissociating state of NO+ +. On the basis of the comparison with calculated energies, the three stable states of NO+ + with energies at 38.6, 40.0, and 42.5 eV were assigned to, respectively, the X 2Σ+, A 2Π, and B 2Σ+ electronic states. The detected emission was ascribed to a B 2Σ+→X 2Σ+ emission around 3170 Å.